The rotation into the mass eigenbasis of the scalar fields in eq. REF  modifies all SM Higgs couplings by a factor of \( \cos \phi \) . The Higgs signal strength, defined as the production cross-section times branching ratio (BR) normalised to the SM prediction, \( \mu := ( \sigma \times \text{BR} )_{\text{obs}} / ( \sigma \times \text{BR} )_{\text{SM}}\)  for a given Higgs production and decay mode, is then predicted to be \( \mu = \cos ^2 \phi \)  irrespective of the mode. The ATLAS and CMS Run 2 combination results for the global signal strength read \(\mu _{\text{ATLAS}} > 0.92 ,\, \mu _{\text{CMS}} > 0.90\)  at 95 % CL [1]}. The more stringent of the two, \( \mu _{\text{ATLAS}} \) , yields for the Higgs-flavon mixing angle: \( \mathopen {}\mathclose {\left| \sin \phi \right|} < 0.28\) . This limit on \( \sin \phi \)  is independent of the flavon mass.
